There have been proposed display systems which allow plural users to conduct operations on one screen. With regard to the display systems, International Patent Publication No. WO2010/021240 discloses the following image display apparatus. The image display apparatus includes a display section for displaying objects, a detecting section configured to automatically detect a conflict among plural users about operations to be performed on an object displayed on the display screen. The image display apparatus further includes a processing section configured to, in response to a detection of the conflict carried out with the detecting section, enlarge an object on which the conflict has arisen or move an object on which the conflict has arisen to a common display area of the display section to adjust the orientation of the moved object. Under the situation that plural users conduct a discussion based on one material (one object) displayed thereon, the image display apparatus conducts a control such that the users can view the material easily.
Though International Patent Publication No. WO2010/021240 describes about a stage that plural users conduct a discussion together (referred as a group work), such a discussion held by plural users further has a stage that each of the users individually considers about the discussion (referred as a personal work), additionally to the group work. It is preferable that a display system has operation modes (a personal mode and a group mode) in each of which users can work in a manner suitable to either of those stages.
An influence of an operation on a certain object to another object in each of the personal mode and the group mode can be considered as follows. In the group work, all the operators keep their eyes on an object as an operation target, and every operator recognizes how the object will be operated. Therefore, such the situation does not cause a problem about the influence of an operation on the object to another object.
On the other hand, in the personal work, each of the operators gives attention to objects separately and not every operator recognizes how one of the objects will be operated. Therefore, when a certain operator performs an operation on an object, the operation can affect another object, which sometimes disturbs an operation of another operator. For example, when an object enlarged by a certain operator overlaps with another object to which another operator gives attention, such the operation can disturb operations and considerations to be conducted by another operator. To solve that, under the situation that each of the operators is working individually, it is required to control operations of operators on objects such that an object operation performed by each of the operators does not affect the display state of another object to which another operator gives attention.
As a method of an operation control so as not to affect the display state of another object to which another operator gives attention, there can be considered a method to divide a working area into pieces for respective operators. However, each of the operators hardly passes and receives objects across the border of their working area, which results in limitation of their operation contents. In view of that, a way to control operations such that an object operation performed by each operator does not affect the display state of another object to which another operator gives attention, without dividing the working area, is now desired. The present invention seeks to solve the problem.